protected function loadTableKeys() {
        $tables = DI()->config->get('dbs.tables');
        if (empty($tables)) {
            throw new PhalApi_Exception_InternalServerError(T('dbs.tables should not be empty'));
        }

        foreach ($tables as $tableName => $tableConfig) {
            if (isset($tableConfig['start']) && isset($tableConfig['end'])) {
                for ($i = $tableConfig['start']; $i <= $tableConfig['end']; $i ++) {
                    self::$tableKeys[$tableName . '_' . $i] = $tableConfig['key'];
                }
            } else {
                self::$tableKeys[$tableName] = $tableConfig['key'];
            }
        }
    }